To manufacture containers and/or to fill products into containers, these containers are normally transported to the individual treatment stations in a continuous product flow on transporters, such as conveyor belts, for example. In order to ascertain the presence and/or the position of containers on transporters, triggering light barriers, for example, can be used. When an object passes through the light barrier, a trigger signal is then generated with which a subsequent treatment step and/or a purposeful forwarding of the detected container can be actuated. An inspection process can likewise be triggered or it can be ascertained whether or not a container is being transported in a proper, particularly upright, position.
For example, known from EP 08 01 289 A2 is a horizontal light curtain in which individual light barriers are arranged one behind the other in the conveying direction, so that a container passes through the individual light barriers one after the other. The light barriers are formed with the help of light guides, which are supplied from a common light source, and which are assigned receiver units. The light barriers detect at the height of the mouth area of the respective container type in order to make it possible to distinguish reliably between containers flowing in one behind the other. Detrimental in this arrangement, however, is that it is limited to a specific measurement height and consequently to a specific measuring task and specific container type.
Known from DE 43 05 559 A1 is a vertical light curtain in which a row-like arrangement of light transmitters is arranged on one side of a conveyor belt and a corresponding receiver row is arranged on the opposite side of the conveyor belt. Individual light barriers, arranged one behind the other in the conveying direction, are furthermore provided in order to determine the transport speed of the transport belt and the containers standing thereon. By means of repeated activation of the light transmitters, a container passing through the light curtain is scanned column by column, in order to create a contour grid of the container, with consideration given to the established conveying speed. This consequently involves a coarsely resolving imaging method, whereby each shaded light barrier segment generates the image points assigned to the container. By comparing these image points with “learned” comparison images, different container types can be distinguished from one another on the basis of their contours. Detrimental in this method, however, is that a comparatively large number of image points must be evaluated, so that the speed of the method is limited as a result. The containers must furthermore be a minimum distance apart from one another for the scanning, as a result of which the machine performance is additionally limited.
Vertical or slanted upright light grids are furthermore known from safety technology, for example from DE 103 29 881 A1 and DE 10 2005 030 829 B4, in order, for example, to detect or to distinguish between objects, such as auto bodies, and/or people on conveyor belts. For this purpose, light curtains are stretched transversely to the transport direction of a conveyor belt, whereby light sources are normally operated simultaneously one above another in a plurality of light barrier levels and a control signal is produced in the event of an inadmissible light attenuation level in one or more of the light barrier levels, for example, in order to switch off the production system for safety reasons. Due to the comparatively slow conveying speed in the case of such production processes and to the comparatively large dimensions of the objects or people to be monitored, a multitude of light barrier levels can easily be arranged one above another and evaluated together.
In filling systems, on the other hand, the position of containers with different shapes and sizes must be recognized reliably at comparatively high transport speeds in order for it to be possible to generate suitable control signals for subsequent production steps. For monitoring production sorted by type, height-adjustable light barriers, for example, are then provided that are to be adjusted to the respective container type. When there is a change in the product, adjustment mechanisms are consequently needed, as a result of which additional expenditure of labour results for the operation and servicing. Further disadvantages are the risk of operating mistakes, the only limited reproducibility due to mechanical hysteresis effects and mechanical wear of the adjustment mechanism.
In contrast, in the case of unsorted product processing, normally a plurality of triggering light barriers at different heights are combined together. Due to the comparatively large dimensions of the individual light barrier modules and the then necessary consolidation of individual controllers, there must be limitations when monitoring an unsorted production line in this way. For example, the light barrier modules cannot be arranged one above the other with the desired vertical resolution in a neck area of the containers that is especially important for detecting the position in order to make it possible to determine the position of different container types with sufficient reliability and flexibility.
There is therefore the need for a triggering light grid and a corresponding method for registering the position of containers with reliability and flexibility, with regard to different measuring tasks and container types, that are better than that of the state of the art.
The set task is solved with a triggering light grid according to the present disclosure, comprising a plurality of light barriers that are provided at different height levels with regard to the conveyance path and that have light sources that can be activated separately of one another and that are accommodated in a common housing. In this way, a compact light grid with an especially high vertical resolution level can be provided. Furthermore, the capability to activate the light sources separately allows the selection of different vertical light barrier areas, in order to solve specific measuring tasks. For example, the neck area of a container can be purposefully measured according to the shape and size of the incoming container type in order to ascertain a position of the container in the product flow. A side wall area of the container can likewise be purposefully measured in order to determine a maximum diameter of the container. Measurement signals from different height levels can likewise be registered simultaneously and compared to one another, in order, for example, to distinguish a proper upright position of the container from an improper reclining position.
A triggering unit for generating control signals on the basis of output signals of the light barriers is furthermore provided. It is consequently particularly possible to generate control signals assigned to individual containers. As a result, for example, a subsequent inspection can be adapted to the container type, the container can be purposefully forwarded and/or the container can be measured for a subsequent production step and its position in the product flow can be determined.
The light barriers comprise measurement beams that preferably are aligned parallel to one another. These preferably run transversely to the transport direction of the assigned conveyance means. On the basis of the capability for separated activation of the light sources, only those light sources have to be operated, and only those respective associated output signals of the respectively operated light barriers have to be evaluated, that are needed for a specific measuring task, for example, the determination of the position in the product flow. In this way, the measurement data processing can take place faster than in the case of a triggering light grid of the known construction, in which all light barrier levels are activated simultaneously and each of their output signals is evaluated. It is consequently possible to implement optimised combinations of individual light barriers with regard to a particular measuring task. For example, in one area of the light grid in which only a low vertical resolution level is needed, it would be possible to activate only every second or third light source.
The triggering unit is preferably formed for selective processing of individual output signals, particularly in order to process only output signals from those light barriers whose light sources have been activated. In this way, the processing time needed for the output of trigger signals can be adapted to the respective measuring task and, in particular, minimized. In particular, it is also possible for a plurality of measuring tasks to be solved simultaneously by means of activating light barriers in different height areas of the triggering light grid in groups and reading out and/or processing their output signals in groups. The number of light barriers needed for a measuring task and their resolution can hereby be adapted with the greatest possible flexibility without mechanical adjustment.
In an especially advantageous embodiment of the triggering unit according to the present disclosure, the output signals of selected light barriers can be evaluated together periodically within measurement cycles, each lasting a maximum of one millisecond, particularly in order to assign at least one individual control signal to each individual container. A control signal, for example, in the form of a suitable trigger edge, can consequently be output within one millisecond of the attenuation or interruption of the triggering light grid. This allows a sufficiently high response speed of the triggering light grid even at the transport speeds for containers customary in filling systems. To be understood as a control signal assigned to an individual container is a control signal that allows purposeful control of a subsequent production step or inspection step and/or purposeful forwarding or ejection of the container with regard to the product flow. The control signal can comprise characteristic information regarding the position and/or size of the container and or information regarding the proper or improper alignment of the container with respect to the product flow. The control signal is, in particular, a switch signal or trigger signal for a production unit or transport unit for the processing, inspection and/or filling of the containers. The control signal can be output both as a digital signal and via a bus with real-time capability, in which the control signal can be transmitted within a millisecond to the respective destination address for actuating an action.
Each of the output signals of the light barriers can be converted into logically usable measurement signals. A logically evaluable signal is understood, for example, as a status signal that, after comparison of the output signals with threshold values or the like, indicates whether or not an admissible light attenuation level in the area of a light barrier has been exceeded.
The triggering unit is preferably formed to evaluate and/or logically combine the output signals, in groups, of selected light barriers, or to generate at least two control signals assigned to a single container. In this way it is possible to combine different measurements within a single measurement cycle. For example, a first measurement can be made with a first light barrier group and simultaneously a second measurement can be made with a second measurement barrier group. The results of the light barrier groups can be evaluated independently of one another and/or compared to one another. This makes it possible, for example, to carry out a plausibility check or to attain additional information by combining measurement results. For example, by comparing the light attenuation level in an area of the container bottom and an area of the container neck, it can be ascertained whether or not a container is standing upright or is being transported in a reclining or slanted position. A position of the container, particularly with regard to a container main axis, can likewise be simultaneously determined and a characteristic container dimension, for example, a maximum diameter, can be determined simultaneously.
Individual measuring tasks can be combined in any way by forming groups of the activated light barriers. The resolution in individual light barrier groups can also be adapted purposefully depending on the measuring task that is to be solved. Furthermore, all light barriers of the triggering light grid can be used together, all light barrier levels of the triggering light grid can be distributed into groups or only selected light barriers of the triggering light grid can be grouped in a suitable manner for one or more measuring tasks. The number of light barriers needed for a specific measuring task, and consequently also the response time of the triggering light grid, can hereby be minimized.
In a particularly advantageous embodiment of the triggering light grid according to the present disclosure, the distance between neighbouring light sources amounts to a maximum of 10 mm, particularly a maximum of 5 mm. As a result, particularly critical container sections, such as neck areas of preserved food jars, for example, can also be measured with sufficient local resolution. This is particularly made possible by the combination of a plurality of light barriers in one shared housing. The shared housing allows an especially dense staggering of individual light barrier levels. The maximum distance is defined in each case between the optical centre axes of the light sources. Suitable light sources are LEDs, for example.
The triggering light grid preferably comprises at least one reflector in order to reverse measurement beams emitted by the light sources back towards the shared housing. In this way, active components, such as both the light sources and also assigned light receivers, can be accommodated compactly in a shared housing. This reduces the expenditure for the cabling and associated plug-in connections. Furthermore, because of the beam reversal, the measurement beams can be guided through the measurement field twice in the area of the conveying section. In this way, the measuring sensitivity and/or the actuation reliability of the triggering light grid can be improved when passing containers with low beam attenuation. Also within the scope of the present disclosure, however, is an arrangement in which the light sources are accommodated in a first shared housing and assigned light receivers are accommodated in a second shared housing. In this case, it is also possible to arrange the light sources and the light receivers on different sides of the conveyance path, so that the measurement beams pass through the measurement field in the area of the conveyance path only once.
The triggering unit is preferably formed to generate a control signal if at least one of the output signals corresponds to light attenuation of at least 5%, particularly of at least 25%, in the assigned light barrier. This allows the detection of transparent media. Because the measurement beams are normally attenuated by several percent with each interface transition of the measurement beams from air into the container wall and from the container wall into air, the measurement of transparent containers is possible with a high level of reliability, particularly when a plurality of light barrier levels are grouped together.
The light sources are preferably provided such that they are offset in the transport direction of the containers. For example, the measurement resolution can be increased in the vertical direction by having every second light source offset in the lateral direction. It is also conceivable hereby that the light sources are provided such that they are only offset with respect to one another in a height area provided particularly for this.
The object according to the present disclosure is furthermore solved with a method for registering the position of containers and/or for checking their alignment on a conveyance path in accordance with Claim 9. By means of the selective activation of individual light barriers and the evaluation of the associated output signals, different measuring tasks can be solved and/or specific measuring tasks can be adapted to different container types, by means of determining the light attenuation level in the stipulated height areas of the conveyance path. The comparison of the determined light attenuation level with at least one comparison value furthermore allows the generation of control signals in order to control purposefully individual containers on the basis of the comparison. This allows flexible product control in the case of both sorted and unsorted conveyance. In particular, there is no longer a need for a mechanical adjustment of different light barrier levels in order to generate trigger signals for changing measuring tasks and/or changing container types.
The height area is preferably given in dependence on a conveyed container type. For example, measurement ranges for determining the position of a container, for determining the diameter and/or for checking a correct conveyance orientation, particularly in the case of sorted conveyance, can be adapted to the respective container type and the time required for actuating a trigger signal can be minimized. However, a plurality of height areas can also be measured simultaneously, particularly in the case of unsorted conveyance, and an automatic detection function can be derived from the output signals of the respective height areas. For example, a container can be identified by a comparison of the output signals of a plurality of light barrier groups and simultaneously measured.
Values of the light attenuation levels in at least two height areas are preferably compared and/or logically processed together in order to determine a container type and/or to distinguish a correct conveyance orientation from an incorrect conveyance orientation. Plausibility checks can likewise be carried out by means of comparison of the output values of different height areas. A correct conveyance orientation is, for example, given in the case of a container that is standing upright. Incorrect conveyance orientations can be given, for example, by a reclining or a slanted upright container position.
Time points of the interruption and release of the light barriers are preferably measured in at least two height areas and calculated together, in order to determine the position of a reference point, a reference surface and/or the main axis of the containers. This allows a localization of axes of symmetry of the containers and the like, even in the case of a measurement on slanted upright container areas. For example, measurement results offset in time can be interpolated in order to improve the precision of a central triggering in the case of slanted upright container walls.
In an especially advantageous development of the method according to the present disclosure, the output signals are evaluated in groups assigned to height areas in order to determine at least two of the following parameters of the container by means of the light attenuation levels at different height areas: height; position in the product flow; characteristic contour; outer diameter; and upright/reclining conveyance position. A plurality of measuring tasks and/or complex measuring tasks can consequently be solved within a single measurement cycle. By means of purposeful activation of the light barriers of the respective height areas, the measurement signals can be optimized for the respective measuring tasks, the measurement signals can be evaluated in a particularly short time and the associated trigger signals can be actuated in a particularly short time.
The control signal is furthermore preferably generated on the basis of a measured displacement increment that is characteristic for the conveyance path, particularly for determining a container position and/or a container diameter. This allows an especially swift and flexible determination of container-typical parameters.
Advantageous embodiments of the present disclosure are depicted in the drawing.